Board clamp mechanism for lift truck equipped with pusher

ABSTRACT

In a lift truck equipped with a pusher mechanism, the lift frame is provided with a pair of board clamp assemblies located above the rear end of the fork arms. Each clamp assembly includes a shoe which is mounted for pivotal motion in a fore-and-aft direction. When a board is received on the fork arms and moved rearwardly, it rotates the shoes of the clamp assemblies rearwardly so that the shoes rest on and engage the top of the board. When the pusher pushes a load off the board, a slight forward movement of the board brings the shoes into tight locking engagement with the board, securing it in place on the fork arms. When the pusher is returned to its retracted position, it engages the shoes and rotates them rearwardly to the release position, so the board can be removed.

United States Patent 11 1 Allegretti et a].

[ BOARD CLAMP MECHANISM FOR LIFT Primary Examiner-Albert J. Makay TRUCK EQUIPPEI) WITH PUSHER Attorney, Agent, or FirmDawson, Tilton, Fallon & [75] Inventors: Anthony J. Allegretti, LaGrange Lungmus Park; Donald R. Duzinkas, Western Springs, both of Ill (57] ABSTRACT [73] Assignee: W. F. Hall Printing Com y, In a lift truck equipped with a pusher mechanism, the

Chicag0 l]| lift frame is provided with a pair of board clamp assemblies located above the rear end of the fork arms, [22] Filed June 1974 Each clamp assembly includes a shoe which is [2 l Appl. No.: 483,639 mounted for pivotal motion in a fore-and-aft direction. When a board is received on the fork arms and moved rearwardly, it rotates the shoes of the clamp assem- 214/514 3 3; blies rearwardly so that the shoes rest on and engage 58 i 655 the top of the board. When the pusher pushes a load l o are 5 3 5 off the board, a slight forward movement of the board brings the shoes into tight locking engagement with the board, securing it in place on the fork arms When [56] Reieremzes cued the pusher is returned to its retracted position, it en- UNITED STATES PATENTS gages the shoes and rotates them rearwardly to the re- 2,37l,66l 3/1945 Wilms r r v r r r. 214/514 lease position, so the board can be removed. 3,l97,053 7/[965 Faust 214/5l4 5 Claims, 3 Drawing Figures 22 2 -a. q I" 'lll" i i i a: I l 26 l' L 2- ll 1 I ll- Ii a l I I IO 0 "l 'l III 25 E I ll BOARD CLAMP MECHANISM FOR LIFT TRUCK EQUIPPED WITH PUSI'IER BACKGROUND AND SUMMARY The present invention relates to a clamp mechanism for securing a platform board to a lift truck which is equipped with a pusher.

Lift trucks, of course, are used in many industries as a means of moving heavy loads relatively short distancesfor example, from a production area to a loading area for shipment. In some applicationsthe food industry and the printing industry to name only twosuch lift trucks are equipped with load pushing mechanisms, simply referred to as load pushes", for pushing the load off the fork arms. For example, in the printing industry wherein the mail is relied upon for distribution, the material may be placed in mail sacks in the production area. These mail sacks are then placed on flat support platforms or boards". The boards are used as a temporary support for a number of mail sacks.

When a board contains a number of mail sacks, a lift truck is used to transport the board and sacks directly into a truck. A load push is then used to urge the sacks forwardly off the board and into the truck along with a number of similar sacks. Thus, the board is available for re-use at the production area, and the loading of sacks into the truck in this loose manner is much more efficient.

Heretofore, the mechanisms used in retaining a board on the fork arms while the pusher urges the load off of the board have been very expensive. One such mechanism includes a horizontal bar spaced slightly above the rear of the fork arms and selectively urged downwardly by a pair of hydraulic cylinders for engaging the board and holding it in place. When the hydraulic cylinders are reversed, the board is unlocked.

Such known gripper mechanisms, in addition to being expensive, suffer the disadvantage that their availability is subject to the availability of components, the supply of which has been known to fluctuateparticularly hydraulic fittings and the hydraulic cylinder and piston rod units. Further, there is the disadvantage that manufacturers have been unwilling to retro-fit an existing lift truck with even these more expensive pusher mechanisms.

The present invention provides for a clamp assembly which mounts directly to the fork arms carried by the lift frame. Preferably two such assemblies are provided, one on either side of the lift frame and above a respective fork arm, if there are two fork arms.

Each clamp includes a shoe which is pivotally mounted for motion in a fore-and-aft direction. When the shoe is rotated rearwardly, it rises and assumes a release position; conversely when it is rotated forwardly, it is lowered for locking or clamping a board in place. Thus, when a board is received on the fork arms and moved rearwardly, it rotates the shoes of the clamps rearwardly so that the shoes rest on top of and engage the board. When the pusher pushes a load off the board, a slight forward movement of the board brings the shoes into tight locking engagement with the board, thereby securing it in place on the fork arms and permitting the pusher to move the load off the board.

When the pusher is returned to its closed position, it engages the shoes and rotates them rearwardly to the release position, so that the board can be removed for reuse.

The present invention therefore provides an economical yet reliable means for clamping a board to the lift frame of a truck while permitting a pusher mechanism to push loads off the board. Further, the present invention is free of elements or units such as hydraulic fittings or cylinder and piston rod units whose supply varies. Still further, the present invention is easily mounted on existing lift trucks and no special expertise is required for retrofitting a truck already in use.

Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.

THE DRAWING FIG. 1 is an upper perspective view, taken from the front and side, of the forward end of a lift truck, shown in fragmentary form, which incorporates the present invention;

FIG. 2 is a fragmentary side close-up view of a clamp assembly constructed according to the present invention and receiving a board; and

FIG. 3 is a view similar to FIG. 2 illustrating the clamp assembly in a release position.

DETAILED DESCRIPTION Referring then to FIG. 1, the forward portion of a lift truck is shown in fragmentary form, and generally designated by reference numeral 10. It includes a pair of forward wheels, one of which is shown at 11, and a lift frame generally designated by reference numeral 12. Conventional mechanism is provided for raising and lowering the lift frame 12 relative to the truck 10.

In the illustrated embodiment, the lift frame 12 is provided with a fork attachment 15 including first and second forwardly extending fork arms 16. As best seen in FIGS. 2 and 3, the fork attachment 15 is secured to the lift frame 12 by means of enlarged hook members 20.

The lift frame 12 is also equipped with a load pusher generally designated 22. The load pusher 22 includes a load-engaging forward wall 23, a scissors link mechanism 24, and a pair of hydraulic cylinder and piston rod units, not shown. The load pusher 22 is conventional, and briefly, it operates under control of the operator to selectively extend the wall 23 between a forward or expanded position and a rear or retracted position. When urged in the forward direction, it pushes a load indicated at L off of a board B. The board B may take any number of forms, including wood, as shown, or metal; and it need not necessarily even be rigid. Its principal function is to act as a temporary support for one or more individual load elements. When the load is pushed off the board B for example, into a truck for transportation, it is desired that the board B be held to the lift frame and be available for re-use.

Toward this end, the present invention provides a pair of clamp assemblies, one associated with each of the fork arms 16. One such clamp assembly is generally designated by reference numeral 25 in FIG. I, and it is mounted to the fork attachment 15 directly above the right-hand fork arm 16, as illustrated. Since the other clamp assembly may be identical, it need not be described for a complete understanding of the invention. In the illustrated embodiment, the clamp assemblies are mounted to the fork attachment, as mentioned. However, it will be appreciated that they could equally well be mounted on the lift frame since they are. in both cases, carried by the lift frame in fixed relation to the fork arms or other load support elements.

Briefly, the clamp assembly includes a bracket 26, a pivot pin 27, and a shoe 28. The bracket 26 comprises a mounting plate 30 to which are welded first and second spaced braces 31, 32. The braces 31, 32 extend forwardly of the mounting bracket 30; and in the illustrated embodiment, as mentioned. the bracket 30 is welded to the forward surface of the hook mount 20 of the fork attachment 15.

The braces 31, 32 are provided with aligned apertures through which the pivot pin 27 is mounted. Thus, in general, the bracket 25 provides a trunnion mount for the shoe 28. The shoe 28 has the general shape of an inverted T, including a base member 35 which may be welded to the pivot pin 27 and a laterally transverse gripper element 36.

As seen in the drawing, the gripper element is curved so that its lower surface 38 is slightly convex. The surface 38 engages the upper surface of the board B to hold it against the fork arms 16 in the locking position; and in order to provide greater friction, the surface 38 may be sprayed by carbide to increase friction. The gripper element 36 may be formed by cutting it from a segment of metal tubing having an outside diameter of 2 "/8 inches and a wall thickness of one-quarter inch. It may be secured to the base member 35 by welding.

The lower portion of the push plate 23 is provided with an angle iron 40 extending transverse of the fork arms 16. At the rear surface of the vertical portion of the angle iron 40, bumper members 41 are welded in alignment with the base 35 of the shoes 28. As illustrated in FIG. 3, when the pusher unit is retracted, the bumper member 41 engages the base 35 of the shoe 28 and rotates it rearwardly about the axis of the pin 27, thereby causing the shoe to disengage the board B and permit it to be removed in the direction of the arrow 45. in FIG. 2, when it is desired to insert the board B (which may be accomplished by moving the fork arms 16 beneath the board B), any relative movement of the board B in the direction of the arrow 46 may be easily accomplished because the shoe 28 is thereby moved towards its release position. However, if the pusher member is moved forwardly, the board B cannot be re moved because any forward motion thereof will cause a clockwise rotation of the shoe 28, thereby increasing the frictional gripping of the rear edge of the board B.

It will be observed from FIGS. 2 and 3 that the distance from the axis 27A of the pivot pin 27 to the engagcment surface 38 of the shoe 28 is greater than the distance from the axis 27A to the top surface of the board 8 when it is inserted. With this provision, there is created an over center lock whereby if it is attempted to withdraw the board 8, the downward force exerted by the shoe 28 in its frictional engagement with the board B increases substantially and strengthens the locking grip on the board.

Having thus described in detail a preferred embodiment of the invention, persons skilled in the art will be able to modify certain of the structure which has been illustrated and substitute equivalent elements for those disclosed while continuing to practice the principle of the invention; and it is, therefore, intended that all such modifications and substitutions be covered as they are embraced within the spirit and scope of the appended claims.

We claim:

1. In combination with a lift truck including a lift frame, forwardly-extending load support means extending from the lower end of said lift frame, and a pusher mechanism carried by said lift frame and extendible above said load support means to push a load off a board carried by said load support means, the improvement comprising: a clamp assembly carried by said lift frame and including a downwardly-depending shoe member; and means for mounting said shoe member for rotation about a horizontal axis transverse of the direction of extension of said pusher means and spaced above said load support means for receiving a board when said board is pushed in a rearward direc tion onto said load support means, the vertical distance between the upper surface of the board received on said load support means and the axis of rotation of said shoe means being less than the distance between said axis and the location at which said shoe means engages said board, whereby when said board is urged for wardly of said load support means, the forward rotation of said shoe means causes it to move forwardly and downwardly to lockingly engage the inserted edge of said board between said shoe means and said load support means.

2. The apparatus of claim 1 wherein said pusher means further includes bumper means adapted to engage said shoe means when said pusher means is in a fully retracted position to rotate said shoe means rearwardly to a release position, thereby permitting removal of said board.

3. The apparatus of claim 1 wherein said clamp assembly comprises a bracket secured to a fork attach ment and said assembly defines first and second for weirdly-extending braces spaced laterally apart; and means for pivotally mounting said shoe means to said braces.

4. The apparatus of claim 3 wherein said shoe means comprises a rigid member having an inverted T-shape with a base pivotally mounted to said braces and a lower cross bar adapted to engage said board in locking relation, the lower surface of said cross bar being convex and treated to enhance the frictional engagement of said board,

5. The apparatus of claim 1 further comprising a second clamp assembly carried by said lift frame for engaging said board at a second position spaced laterally from the location of said first-named clamp assembly. 

1. In combination with a lift truck including a lift frame, forwardly-extending load support means extending from the lower end of said lift frame, and a pusher mechanism carried by said lift frame and extendible above said load support means to push a load off a board carried by said load support means, the improvement comprising: a clamp assembly carried by said lift frame and includIng a downwardly-depending shoe member; and means for mounting said shoe member for rotation about a horizontal axis transverse of the direction of extension of said pusher means and spaced above said load support means for receiving a board when said board is pushed in a rearward direction onto said load support means, the vertical distance between the upper surface of the board received on said load support means and the axis of rotation of said shoe means being less than the distance between said axis and the location at which said shoe means engages said board, whereby when said board is urged forwardly of said load support means, the forward rotation of said shoe means causes it to move forwardly and downwardly to lockingly engage the inserted edge of said board between said shoe means and said load support means.
 2. The apparatus of claim 1 wherein said pusher means further includes bumper means adapted to engage said shoe means when said pusher means is in a fully retracted position to rotate said shoe means rearwardly to a release position, thereby permitting removal of said board.
 3. The apparatus of claim 1 wherein said clamp assembly comprises a bracket secured to a fork attachment and said assembly defines first and second forwardly-extending braces spaced laterally apart; and means for pivotally mounting said shoe means to said braces.
 4. The apparatus of claim 3 wherein said shoe means comprises a rigid member having an inverted T-shape with a base pivotally mounted to said braces and a lower cross bar adapted to engage said board in locking relation, the lower surface of said cross bar being convex and treated to enhance the frictional engagement of said board.
 5. The apparatus of claim 1 further comprising a second clamp assembly carried by said lift frame for engaging said board at a second position spaced laterally from the location of said first-named clamp assembly. 